Conventional air-conditioning apparatuses perform defrosting operation by inverting a refrigerant cycle to remove frost in an outdoor heat exchanger acting as an evaporator in a heating operation. However, in that defrosting operation, indoor comfort decreases because heating is halted in the defrosting operation. One example of a technique capable of performing a heating operation and a defrosting operation at a time is a heat pump including an outdoor heat exchanger divided into a plurality of parallel heat exchangers, a bypass that bypasses gas discharged from an injection compressor for each of the divided heat exchangers, and an electromagnetic on-off valve that controls a bypass state (see, for example, Patent Literature 1).
That heat pump includes an outdoor unit, indoor units, and a main pipe connecting them such that a refrigerant circulates therethrough and is a multi-type air-conditioning apparatus in which two indoor units are connected to one outdoor unit. The outdoor unit includes an injection compressor, a four-way valve for switching between a cooling operation and a heating operation, outdoor heat exchangers connected in parallel, a first bypass pipes having a first end connected between the injection compressor and the four-way valve and a second end split and connected in parallel to the pipes connected to the outdoor heat exchangers, a second flow switching device for switching the flow of the refrigerant to either one of the main pipe and the first bypass pipe, and a third flow control valve for controlling the flow rate of the refrigerant flowing in the first bypass pipe. That enables continuous heating without inverting the refrigeration cycle by causing part of the refrigerant from the injection compressor to alternately enter each of the bypasses and by alternately defrosting each of the parallel heat exchangers.
There is a refrigeration machine that includes a plurality of parallel heat exchangers, a plurality of main compressors, and a sub compressor and that injects a refrigerant used in deicing for the heat exchanger into the sub compressor (see, for example, Patent Literature 2).